Zirconium-REE mineralization characteristic in Sakju and Ryongpho intrusions of Sakju Complex distributed in the western area, DPR Korea

Abstract

Alkali intrusions of Sakju Complex distributed in the western area, DPR Korea were formed in mid-Proterozoic era. The Zirconium-REE mineralization occurs in Sakju and Ryongpho intrusions of Sakju Complex. Zr and Hf are the typical lithophile elements and always exist together under the closed relation to alkali and acid igneous rock. In our country, Zr and Hf mineral resources are exploited in the coast placer deposits and some in the alluvial placers. In addition, deposits related to alkali syenite, carbonatite and pegmatite deposites are found. The contents of Zr, Hf and REEs in intrusions of the Sakju complex are much higher than the average contents of the earth's crust and those in alkali rocks. The REE values in the constituent rocks of Ryongpho intrusion, from earlier differentiation phase to later phase, gradually decrease in the order of alkali pyroxenite to alkali gabbro to alkali amphibole syenite to alkali feldspar syenite. The constituent rocks have the similar chondrite-normalized REE distribution patterns, i.e., rich in LREE and deficient in HREE, and no or weak negative anomaly of Eu. REEs are concentrated in the fluorite zone experienced Ca–F metasomatism in alkali pyroxenite and alkali gabbro to form a medium-high grade REE ore body. The carbonatite in Sakju intrusion and alkali metasomatic belts heavily experienced the albitization in Ryongpho intrusion are unique useful mineral resources capable of recovering simultaneously Hf, Sr, REEs as well as Zr.